1. Field of the Invention
The present invention relates to a biopsy needle set for sucking and collecting tissue sections in diseased parts such as internal organs and the like of a patient for obtaining test specimen, and particularly to a biopsy needle set which can suck certainly tissue sections and maintain stably the suction force during removal of such needle from the human body.
2. Description of the Prior Art
As a conventional biopsy needle set, there has been proposed, for example, a collecting instrument of internal organ tissue sections, as shown in Japanese Patent Publication No. 52575/1981, which comprises, as illustrated in FIGS. 1 through 4, a metallic outer needle 1 an end of which is formed into an edge of blade and which is provided with a needle base 2 at the opposite end thereof, a syringe barrel 3 to an end of which the needle base 2 is detachably attached, an inner needle 4 an end of which is formed into a sharp tip portion 4a, a slidably contacting portion 4b having a diameter a little less than a inner diameter of the outer needle 1 extending from said sharp tip portion 4a, and a flat supporting portion 4c extending further from said slidably contacting portion 4b, and a syringe plunger 6 on an end of which mounts a slide packing 5 fitted closely in the inside wall of the syringe barrel 3 to slidably move therein, the inner needle 4 being provided on the end of said syringe plunger 6.
In the above construction, a human body is punctured with the biopsy needle set under such condition where the sharp tip portion 4a of the inner needle 4 is projected from the outer needle 1 and when the sharp tip portion 4a reaches an internal organ, the syringe plunger 6 and the inner needle 4 are relatively retracted from the syringe barrel 3 and the outer needle 1, so that negative pressure is produced in the syringe barrel 3 by withdrawal of the slide packing 5 fitted closely in the syringe barrel 3. Thus, such negative pressure is transmitted to the end of the outer needle 1 through a gap defined between the outer needle 1 and the inner needle 4 and when the syringe barrel 3 is advanced while maintaining the condition as mentioned above, the blade edge of the outer needle 1 cuts off the tissue in a columnar shape. Then, a part of the internal organ which has been in contact with the end of the outer needle 1 is sucked to be led into the outer needle 1. In this state, when the retraction of the syringe plunger 6 is stopped and the outer needle 1 is withdrawn from the body, the tissue sections being in the outer needle 1 as a result of the suction are torn off so that such tissue sections can be taken out from the body.
According to the above conventional example, the slidably contacting portion 4b is formed at the end portion of the inner needle 4, and the gap is defined between the supporting portion 4c extending from the slidably contacting portion 4b and the inside wall of the outer needle 1, such that the supporting portion 4c is not in close contact with the inside wall of the outer needle 1 ,whereby negative pressure produced in the syringe barrel 3 can be efficiently transmitted to the end of the outer needle 1. Hence, when an internal organ to be colleted is merely punctured slightly with the end of the outer needle 1, a test specimen can be collected so that pain in a patient can be abated. In case of collecting tissue sections, a thick needle having a diameter of 1.05 mm (19 G) or more has been used as the outer needle 1 of a conventional biopsy needle.
In accordance with such conventional collecting instrument of internal organ tissue sections, however, negative pressure transmitted to the end of the outer needle 1 keeps leaking at the slidably contacting portion 4b in case of suction by the syringe plunger 6, so that if it is intended to produce intensive suction force at the end of the outer needle 1, the syringe plunger 6 must be rapidly pulled. Thus there have been such disadvantages that the collection of test specimens becomes unreliable, and that in the case where outer needle 1 is made more slender for abating pain in a patient, only a tissue liquid except tissue sections may be collected because of the weak suction force.